The basic objectives of this proposal are to provide new information on the conformation and mechanism of reaction of the bovine heart phosphatidylcholine exchange protein. Using established synthetic methods it proposed that a fluorescent phosphatidycholine be synthesized with anthranoylstearic acid as the fluorescent chromophore. This fluorescent phosphatidylcholine will be incorporated into phosphatidylcholine liposomes as a vehicle for fluorescently labeling the exchange protein. The fluorescent lifetime and decay of emission anisotropy of the fluorescently labelled exchange protein will be measured by time resolved methods using a simple photon counting nanosecond fluorimeter. Emission anisotropy decay will be analyzed to provide information about the overall conformation of the exchange protein, and to obtain information about the phospholipid binding site in the solution and membrane bound states of the protein. Energy transfer experiments are also proposed for membrane bound exchange protein, with the objective of determining the degree of penetration of the protein into the donor liposome membrane.